1. Field of the Invention
The present invention provides ultra-intense laser pulses capable of interacting with matter, and more specifically, it relates to a chirped pulse amplification system and a method that includes lengthening a pulse's duration by often using cascaded pairs of gratings so as to increase the angular dispersion and produce a high power, short pulse.
2. Description of Related Art
The conventional method for circumventing optical damage due to amplification of high intensity pulsed sources is accomplished by chirped pulse amplification (i.e., CPA).
Chirped pulse amplification originated 60 years ago during the development of microwave radar. In the optical case, one avoids intensity-dependent damage by increasing the input temporal pulse duration prior to amplification by passing an input pulse through a frequency-dependent delay line. Such a dispersive delay line often includes prisms or gratings to separate the spectral content of the pulse and in doing so produce an optical path difference for different spectral components and thus stretch the pulses temporally prior to amplification and compress them afterwards. By amplifying a stretched pulse, higher peak intensity can be achieved without reaching the damage threshold of the amplifying material.
The required footprint of CPA pulse compressors and stretchers is approximately inversely proportional to the dispersion of the dispersive element and to the bandwidth of the pulse being stretched. For a given wavelength, however, the dispersion of a grating is a function of the groove density, which cannot be arbitrarily increased and still obtain a solution to the grating equation. Thus the dispersion of the gratings is limited, and the footprint is determined by the bandwidth of the pulses being stretched.
For CPA of pulses with transform-limited pulse widths in the picosecond regime, where the bandwidth of the pulse is low, grating compressors with grating separations of several meters are not uncommon, and prism compressors are impractical due to their even lower dispersion and greater length. Even with grating-based compressors, application of CPA to materials such as Nd;YAG and Nd:YLF, whose bandwidth limits compressed pulse durations to of order of about 5 ps or greater requires impractically large grating separations or extensive folding of the optical path.
Accordingly, a need exists for a configuration that can increase CPA compressor dispersion at high efficiency use angles so as to produce compact configurations. The present invention is directed to such a need.